1. Field of the Invention
The present invention relates to a leadless type resin-sealed semiconductor package having no outer leads outwardly extending from a periphery thereof, and a production process for manufacturing such a leadless type resin-sealed semiconductor package.
2. Description of the Related Art
In general, a conventional resin-sealed semiconductor package includes an island or plate-like mount, a semiconductor chip securely mounted on the plate-like mount and having a plurality of electrode pads provided on a top surface thereof, a plurality of leads electrically connected to the respective electrode pads of the semiconductor chip through the intermediary of bonding wires, and a molded resin enveloper encapsulating and seating the plate-like mount, the semiconductor chip, and the inner portions of the leads, with the outer portions of the leads outwardly and laterally extending from sides of the molded resin enveloper. The resin-sealed semiconductor package is mounted on a suitable wiring board such that the outer portions of the leads are electrically contacted with and bonded to electrode pads provided and arranged on the wiring board.
Of course, this resin-sealed semiconductor package is undesirable in application to a miniature or compact piece of electronic equipment in that the outwardly and laterally extending outer portions of the leads result in overall bulkiness of the resin-sealed semiconductor package.
A leadless type resin-sealed semiconductor package has been developed to be more compactly arranged in comparison with the aforesaid conventional resin-sealed semiconductor package. In particular, the leadless type resin-sealed semiconductor package includes an island or plate-like mount, a semiconductor chip mounted on the plate-like mount and having electrode pads provided on a top surface thereof, a molded resin enveloper encapsulating and seating the semiconductor chip, and electrode pads provided on the molded resin enveloper and electrically connected to the electrode pads of the semiconductor chip. The leadless type resin-sealed semiconductor package is mounted on a suitable wiring board such that the electrode pads provided on the molded resin enveloper are electrically contacted with and soldered to electrode pads provided and arranged on the wiring board, using a suitable solder paste.
Nevertheless, this leadless type resin-sealed semiconductor package fails to obtain a sufficient mounting strength between the semiconductor package and the wiring board. In particular, when each of the electrode pads provided on the molded resin enveloper is soldered to a corresponding electrode pad provided on the wiring board, a solder fillet is produced between the soldered electrode pads. The soldering strength of the soldered electrode pads, and therefore, the mounting strength between the semiconductor package and the wiring board, is evaluated by both an extent and a configuration of the produced solder fillet. However, in the conventional leadless type resin-sealed semiconductor package, the extent of the solder fillet is relatively small, and it is difficult or troublesome to visually inspect the configuration of the solder fillet, as explained in detail hereinafter.
JP-A-2001-077268 discloses a leadless type resin-sealed semiconductor package, which is constructed so that a large mounting strength can be obtained when the leadless type resin-sealed semiconductor package is mounted on a wiring board. Nevertheless, a production process of this semiconductor package involves some additional processes to obtain the large mounting strength, resulting in an increase in production cost therefor, as explained in detail hereinafter.